The present invention relates to an electrophotographic process unit, including a photosensitive member and process means, detachably mounted in an apparatus for forming images.
The concept of a removable process unit was disclosed in U.S. Pat. No. 4,327,992 which discloses a copying apparatus in which the serviceable parts, including a photosensitive member and a developer unit, are mounted on a drawer frame which can be easily withdrawn from the main unit in order that service of the consumable parts might take place.
U.S. Pat. No. 4,538,896 discloses a process unit which is removable from the main image forming unit and is intended to be discarded. This allows the user to perform a preventive maintenance task without specialised assistance from a Service Technician.
GB 2,101,903 discloses a user removable process unit fitted with a cover to shield the photosensitive member. This cover is movable between two positions; the first to expose the photosensitive member for the purposes of image transfer and the second to shield it. Acknowledging that the user is handling a sensitive part of the apparatus and may wish to re-install it at a later date for the purposes of colour changing or clearing a paper jam, the disclosure seeks to provide protection for the photosensitive drum when the process unit is in unskilled hands.
U.S. Pat. No. 4,462,677 discloses a cover which is actuated by the opening of the paper path such as in a clam shell copier arrangement.
U.S. Pat. No. 4,470,689 discloses a cover which is actuated by the removal of the process unit from the image forming apparatus.
The latter three documents disclose embodiments which require a discrete actuating system which is not part of the image forming mechanism to effect the opening or closing of the drum cover. U.S. Pat. No. 6,091,916 discloses a cover which is actuated by the movement of one of the process elements in the image forming system.
The placement of the process unit into the image forming apparatus is critical with respect to both the required positional location of the unit within the apparatus and also the force required to install it. Furthermore the path by which the cartridge is installed has in recent years become more convoluted due to the compact nature of the various machines and also the need to bring various process elements into contact along closely defined vectors. The need to balance the cartridge as it is installed is highlighted in U.S. Pat. No. 5,500,714 where an offset grip is provided to enable better balancing of the process unit as it is inserted.
The invention provides a process unit for use in an electrophotographic image forming apparatus comprising:
a carrying handle;
a photosensitive member;
process means;
a movable cover connected to the process unit and shielding an area of the
periphery of the photosensitive member:
arranged such that the cover is designed to retract from its shielding position before the process unit is installed into the body of the image forming apparatus.
In a particularly preferred embodiment the present invention enables the user to manually open the cover as part of the act of gripping the handle provided an the process unit. Hence the cover is opened prior to the process unit engaging the guideways within the image forming apparatus at which point the balance and attitude of the cartridge become critical.
Thus there are fewer forces on the process unit than in conventional systems whereby an actuator is provided to open the cover during installation; and therefore the user has more control in ensuring accurate positional installation with the minimum of force required.
Two methods are disclosed whereby the user might manually effect the opening of the cover by gripping the handle. The first is a panel levered against the handle and splaying outwards when the cover is in the closed position. When the user grasps the handle he squeezes the panel against the body of the handle and linkages therefrom provide for the opening of the cover.
The second method involves the entire handle being rotationally moveable between two positions. At rest the handle is inclined at a first angle to the process unit and the cover is closed. When the user picks up the unit and extends the unit into the interior of the image forming apparatus, the gravity of the tilting process unit causes the handle to rotate to a second angle which is linked to the opening of the cover.
A beneficial effect of the second method is that the second rotational position of the handle, and therefore the changed attitude of the process unit relative to the handle, allows for an easier and more balanced insertion of the process unit into the image forming apparatus.
The above and other objects and advantages of the present invention shall be made apparent from the accompanying drawings and the description thereof.